The present application claims priority to Japanese Application No. P2000-034379 filed Feb. 7, 2000, which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
This invention relates to a device and a method for image processing, and more particularly, is suitably applicable to, for instance, a video camera.
2. Description of the Related Art
Heretofore, in a video camera, as methods for improving the contrast (the difference between light and shade) and the sharpness (the clearness of the boundaries) of an image that has been captured by a solid state image sensing device (CCD: Charge Coupled Device), a contrast enhancing method by means of gray level transformation and/or a high-frequency components enhancing method wherein the contrast of the high-frequency components in an image is enhanced are known.
As the contrast enhancing method, a method that is called tone curve adjustment wherein the pixel level of each pixel of an image is converted by the use of a function that has the stated input-output relation (hereinafter, this is referred to as a level conversion function) and/or a method that is called histogram equalization wherein the level conversion function is adaptively changed in response to the frequency distribution of the pixel level have been proposed; besides, as the high-frequency components enhancing method, a method that is called unsharp masking has been proposed, wherein so-called outline enhancement is performed, that is, the edges of an image are extracted and then the extracted edges are enhanced.
By the way, in the contrast enhancing method, there has been such a problem that the contrast can be improved with respect to only partial brightness region out of the whole dynamic range (the difference between the maximum level and the minimum level) of an image, and also there has been such a problem that the contrast deteriorates contrarily, at the most bright portion and the most dark portion of the image in the case of tone curve adjustment, and at the vicinity of a brightness region that has little frequency distribution in the case of histogram equalization. Besides, in the high-frequency components enhancing method, there has been such a problem that the contrast of only high-frequency components of an image is enhanced, and so the vicinity of the edges of the image is enhanced unnaturally, and the image quality deteriorates unavoidably.
In view of the foregoing, an object of this invention is to provide a device and a method of image processing which can significantly improve the contrast and the sharpness of the whole image in comparison with the ordinary.
The foregoing object and other objects of the invention have been achieved by the provision of a device and a method of image processing which, while conserving the edges with the pixel values which change abruptly out of input image data, amplifies the portions other than the edges. It is thus possible to enhance the portions other than the edges and display.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.